73 lines
2.1 KiB
C
73 lines
2.1 KiB
C
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// Copyright 2022 The Abseil Authors.
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// https://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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#ifndef ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
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#define ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
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#include <cstdint>
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#include "absl/base/config.h"
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#include "absl/base/internal/endian.h"
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#include "absl/crc/internal/crc32_x86_arm_combined_simd.h"
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namespace absl {
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ABSL_NAMESPACE_BEGIN
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namespace crc_internal {
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// CRC32C implementation optimized for small inputs.
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// Either computes crc and return true, or if there is
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// no hardware support does nothing and returns false.
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inline bool ExtendCrc32cInline(uint32_t* crc, const char* p, size_t n) {
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#if defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) || \
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defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
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constexpr uint32_t kCrc32Xor = 0xffffffffU;
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*crc ^= kCrc32Xor;
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if (n & 1) {
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*crc = CRC32_u8(*crc, static_cast<uint8_t>(*p));
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n--;
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p++;
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}
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if (n & 2) {
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*crc = CRC32_u16(*crc, absl::little_endian::Load16(p));
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n -= 2;
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p += 2;
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}
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if (n & 4) {
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*crc = CRC32_u32(*crc, absl::little_endian::Load32(p));
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n -= 4;
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p += 4;
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}
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while (n) {
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*crc = CRC32_u64(*crc, absl::little_endian::Load64(p));
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n -= 8;
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p += 8;
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}
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*crc ^= kCrc32Xor;
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return true;
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#else
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// No hardware support, signal the need to fallback.
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static_cast<void>(crc);
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static_cast<void>(p);
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static_cast<void>(n);
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return false;
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#endif // defined(ABSL_CRC_INTERNAL_HAVE_ARM_SIMD) ||
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// defined(ABSL_CRC_INTERNAL_HAVE_X86_SIMD)
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}
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} // namespace crc_internal
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ABSL_NAMESPACE_END
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} // namespace absl
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#endif // ABSL_CRC_INTERNAL_CRC32C_INLINE_H_
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